1. Field of the Invention
The invention relates to light transmissive laminates and a method of making them and more particularly to such laminates wherein two or more sheets of light transmissive material are bonded together by means of a thermosetting resinous composition.
2. Description of the Prior Art
Light transmissive laminates are well known. Safety glass which is employed in automobiles and elsewhere is an example of a light transmissive laminate formed from two sheets of glass bonded together by means of an adhesive resinous substance. Aircraft glazing frequently employs multiple layers of glass or similar transparent sheets such as polyermized methylmethacrylate, bonded together by means of a suitable light transmissive adhesive which may be polymerized methylmethacrylate. In the past such laminates have become discolored when exposed to elevated temperatures. The canopy of a jet aircraft, for example, becomes quite hot as the plane moves through the atmosphere at modern airplane speeds. The glazing further is heated significantly when the aircraft is parked on the ground in direct sunlight. After several hundred hours of exposure to elevated temperatures of the order of 300.degree.F, the adhesive binder between the light transmissive sheets deteriorates and the overall light transmissive properties of the laminate are diminished. Discolored glazing can be observed at many present day aircraft storage facilities.
In forming laminates from acrylic polymer sheets, the exothermic reaction of conventional thermosetting bonding resins may create dimensional alterations in the acrylic polymer sheets resulting in vision-distorting deformations.
The present method is especially useful in the production of television picture tubes which require a transparent faceplate and also a transparent safety coverplate.